A large number of signals are input in order to be measured by measurement systems that measure the many properties of LSIs, TFT arrays, and other semiconductor devices, and these systems often integrate and analyze the measurement data using an actuator that is divided into modules responsible for analog measurement and analog-digital conversion (ADC) and a controller part that processes and analyzes the digital data obtained from the modules, as in Japanese Kokai [Unexamined] Patent 2001-52,281.
A typical measurement system having an actuator divided into modules and a controller is described while referring to the structural drawing in FIG. 4 and the time chart in FIG. 5. The system in FIG. 4 comprises measuring apparatuses 150 and 160, modules 250 and 260 connected to these measuring apparatuses, and a controller 350 connected to modules 250 and 260. The solid lines (261, 264) between each structural element in the figure represent the digital signal lines, while the broken lines (151, 161) represent analog signal lines, and the double lines (262, 361, etc.) represent data buses of the digital data. Module 250 comprises an analog-digital converter (ADC) 251 that receives analog measurement signals from the measuring apparatus 150; an FIFO 253 connected to the output of ADC 251; a communications part 254 connected to FIFO 253; and a control part 255 that controls ADC 251 and communications part 254. The internal structure of the other module 260 is the same as that of module 250; therefore, it is not illustrated in FIG. 4. Moreover, the controller 350 comprises communications parts 355 and 356 that receive output data from modules 250 and 260, a memory 352 that houses the received data 354, and a processor 351 that processes these data 354 and finds the measurement and analysis results.
Next, the operation of the above-mentioned measurement system is described. First, when analog measurement signals are input from measuring apparatus 150, ADC 251 notifies that data have been input to control part 255 and converts analog measurement signals to digital data. The system in FIG. 4 is a structure wherein three types of analog measurement signals (represented as a, b, and c in FIG. 5) are output from measuring apparatus 150; therefore, ADC 251 converts these three types of data to digital data in succession and accumulates them in FIFO 253. The same measurement is repeated three times (1a through 1c, 2a through 2c, 3a through 3c) and when the measurements are completed, control part 255 sends a command to transfer data to communications part 254. Thus, communications part 254 transfers the digital data that have accumulated in FIFO 253 to controller 350 in succession. Communications part 355 within controller 350 stores the digital data that have been received in memory 352. The processor 351 begins data processing when these three data (a, b, c) 354 are received and finds the analysis results.
There is a data transfer 265 between module 250 and controller 350 such as shown in FIG. 4.
However, when the noise that is generated by the digital data transfer mixes with analog signal lines 151 and 161, the measurement accuracy deteriorates. Therefore, the data transfer must be performed after analog signal measurement by the measuring apparatus in FIG. 4, as is clear from the timing chart in FIG. 5. However, when this type of measurement sequence is adopted, it requires time to transfer data after the measurement is completed. In addition, controller 350 can only start processing the data when the data transfer is completed. Therefore, there is a large increase in the time that it takes to obtain measurement results once the measurements are started.
It is possible to transfer the data between each measurement (between 1c and 2a and between 2c and 3a) in order to curtail measurement time, but the control part 255 of module 250 does not know the timing by which analog measurement signals are input from measuring apparatus 150. There is a chance that the following analog measurement signal may input during the data transfer and the electric noise caused by the data transfer may have an effect on the quality of the analog data. Consequently, data transfer should not be performed during the analog data measurement.